THURMAN, Iowa — Concerned that Midwesterners might be complacent after repeated tornado warnings came to nothing, forecasters issued a sternly worded alert, well in advance, that weekend storms could prove fatal.

The warnings caught Larry Hill's attention.

The 72-year-old kept an eye on television weather reports and was barricaded inside a closet by the time a tornado ripped the roof off his home in the southwest Iowa town of Thurman.

"We'd been on the lookout for it for three days," he said Sunday morning as he sifted through the remains of his home. "We were as ready as we could have been."

That twister was one of dozens that strafed the region on Saturday and Sunday. The National Weather Service's Storm Prediction Center in Norman, Okla., which specializes in tornado forecasting, had warned more than 24 hours ahead of a possible "high-end, life-threatening event."

In the end, only one proved fatal.

"We can't do this with every event," said the prediction center's Ken Miller, noting that it's not easy to predict which storm systems could pose a threat to life and property.

Miller said he was pleased the warnings were heeded.

"We measure our success by how the public reacts," he said.

National Weather Service offices in Missouri and Kansas are testing more specific warnings based on the severity of a storm's expected impact. On Saturday morning, the weather service in Wichita, Kan., warned that residents "could be killed if not underground or in a tornado shelter.

"Complete destruction of entire neighborhoods is likely," the warning said. "Mass devastation is highly likely, making the area unrecognizable to survivors."

In south central Kansas, Sedgwick County Emergency Management Director Randy Duncan credited the dire language of the warnings for saving lives.

"People become used to those warnings. That is a dangerous complacency," Duncan said. "We need to break through the clutter of everyday noise to get people's attention."

Greg Carbin, a meteorologist at the Storm Prediction Center, said Monday that about 75 tornadoes touched down in four Great Plains states from 7 a.m. Saturday to 7 a.m. Sunday. Most of the tornadoes were in Kansas, followed by Oklahoma, Iowa and Nebraska.

About 100 homes were damaged in a Wichita mobile home park, but no serious injuries or fatalities were reported.

"We knew well ahead of time that this was going to be ugly. People listened," Sedgwick County Commissioner Tim Norton said.

One northwest Oklahoma town was not so fortunate. As a monster twister bore down, cloaked in darkness in Sunday's early hours, Woodward's 20 outdoor tornado sirens did not sound — apparently knocked out when lightning struck a tower used to activate the system.

Frank Hobbie and his daughters, aged 5 and 7 years, died when the tornado hit the mobile home park where they lived, as did Darren Juul and a 10-year-old girl at a home a few miles away.

State medical examiner's office spokeswoman Amy Elliot said no other details were available but that a critically hurt child was airlifted to a Texas hospital.

A third man died at a hospital in Amarillo, Texas, on Sunday night as a result of injuries suffered in the tornado, Woodward County Emergency Management Director Matt Lehenbauer said. Texas. Lehenbauer did not release the man's name or age.

"Our thoughts and prayers just go out to the families that have lost their loved ones, especially the children," said Oklahoma Gov. Mary Fallin, who declared a state of emergency Sunday after touring the damage. "It's always devastating to hear about the loss of life of children."

The Red Cross set up a shelter at a church, but Lehenbauer said some people were sleeping in their yards.

"Some folks want to stay there and keep an eye on their property," he said.

It was not clear if the sirens could have prevented the deaths, had they sounded.

Many residents in Tornado Alley have grown up counting on sirens to warn them when a twister has been spotted on the ground, but emergency officials say that can be one of the least reliable methods, especially when a tornado hits at night.

"An outdoor warning system should never be the only way or even the primary way to receive a warning," said Rick Smith, a warning coordination meteorologist with the National Weather Service. "Our message that we preach is you have to have several ways to receive a warning."

Curt and Andra Raymer had taken steps to prepare, but thought they were in the clear until a television meteorologist warned Woodward residents to take cover just minutes before the storm hit.

"We heard the sirens yesterday afternoon, and they blew for 40 minutes," said Andra Raymer, 44, as she picked through the rubble of her home that was covered with insulation, broken glass and splintered wood. "Last night when this one came through, we didn't hear anything."

The couple and their dogs took shelter in an interior bathroom as the roof was lifted from their home and smashed in their backyard.

"We're just lucky to be alive," Curt Raymer said. "We walked out into the street and just couldn't believe it."

Emergency management officials urged residents to take advantage of weather radios, smartphones and television warnings to keep them up to speed when weather turns dangerous. Sirens are not designed to wake residents who are sleeping or to penetrate the thick insulation in today's homes, said Albert Ashwood, the director of Oklahoma's Office of Emergency Management.

"Sirens are referred to as outdoor warning systems, and that's what they're there for: to tell people who are outdoors to come inside and find out what's going on," Ashwood said.

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